How to restrict movement for a length or period of time (logic bricks)?
You will need to add a Float property to the 'yellow' area. I called mine "Bar". no reason. (if it isn't area you want to determine it by then skip this step and go with a Delay sensor rather than Collision, Near, or Ray)

Use a Collision, Near, or Ray (depending on your preferences and needs)sensor to determine when the "Bar" property is close enough to invoke the constraint behavior.

Via an And controller, link your sensor to a Constraint actuator and set the axis based on whatever axis is "up" in your diagram. Turn on true level triggering on the sensor.